I have a website for example www.site.com, I got also a Google AdWords account, and I got some vouchers from many of my friends around the world.

Now I'm wondering if I can use all these vouchers to promote my website in my AdWords champaign since they are some from USA and some from UK, and as far as I know they should be used in the country were you got them.

I accidentally managed to use two vouchers on one AdWords account: while creating it I entered a voucher code, got an error message and entered another voucher code. After the first payment (which is a requirement for those vouchers), both voucher codes were added to my account.

However, I can't add new voucher codes to this account anymore. This trick only seemed to work while creating the account, and perhaps even that was a glitch from Google.